1. Field of the Invention
The invention relates to a vacuum chamber that has at least one insulating cylinder made from a ceramic material and has end faces that are each covered by a cover. A movable contact piece that is attached to a movable stem is also provided in the vacuum chamber. A vacuum-tight sealing element is fastened between one cover and the movable contact stem to permit the movement of the contact stem.
Such vacuum chambers are customarily used in a switchgear assembly whose gas, such as air, is an insulating gas that is normally at atmospheric pressure. Consequently, the insulating cylinder, the covers and the bellows are configured in terms of strength for atmospheric pressure.
Cases are conceivable in which the vacuum chamber is installed in a switchgear assembly whose pressure is substantially increased, for example up to approximately 25 bars, with the result that the insulating cylinder, the covers and the fastening points of the covers on the insulating cylinder, and the bellows must all be configured such that they withstand this pressure.
2. Summary of the Invention
It is accordingly an object of the invention to provide a vacuum chamber that overcomes the above-mentioned disadvantages of the prior art devices of this general type, which is configured to operate at a high pressure of approximately 25 bars.
With the foregoing and other objects in view there is provided, in accordance with the invention, a vacuum chamber, including:
a plurality of covers each constructed in a cup-shaped fashion and having a main region with a first thickness and a free end with a second thickness being thinner than the first thickness and extending from the main region; PA1 at least one insulating cylinder made from ceramic and having end faces each closed by one of the covers; PA1 at least one support ring disposed between each of the covers and an end face of the end faces of the insulating cylinder, the free end of each of the covers firmly soldered to the end PA1 faces of the insulating cylinder with an interposition of the support ring there-between; PA1 a movable contact stem; PA1 a movable contact piece attached to the movable contact stem; PA1 a fixed contact stem; PA1 a fixed contact piece attached to the fixed contact stem, the movable contact piece attached to the movable contact stem and the fixed contact piece attached to the fixed contact, respectively, penetrating the covers; and PA1 a vacuum-tight sealing element fastened between one of the covers and the movable contact stem and permits a movement of the moveable contact stem, the sealing element having at least one layer connected to the one of the covers and the movable contact stem.
A few specific points are important in the configuration of the vacuum chamber.
First, the cover is to be of a pressure tight configuration and, moreover, stress-compensating configurations of the cover/ceramic connection are to be provided. Only the dimensioning is to be taken into account in configuring the cover. Moreover, because of the increased pressure particular importance also attaches to the sealing element between the cover and the movable contact stem.
It is expedient for the sealing element to be at least a single-layer bellows. In the case of a multi-layer bellows, it is to be ensured that no gas can penetrate from the switchgear assembly into the interspace between the individual layers of the bellows, and this is achieved by welding the joints between layers of the bellows in a gas-tight or vacuum-tight fashion.
The sealing element can, moreover, also contain a plurality of mutually assigned frustoconical rings which resemble disk springs and are connected, in particular welded, to one another in a vacuum-tight or gas-tight fashion at the ends touching one another. The rings can be constructed in this case in one or more layers.
It is also possible to construct the sealing element as a diaphragm cover which has at least one diaphragm layer whose inner and outer edges, in the case of multi-layer configuration, are welded to one another in a vacuum-tight or gas-tight fashion and to the cover and the movable contact stem.
Furthermore, it is also to be ensured that the length of the section of the edge which has the thinner wall thickness is dimensioned such that it absorbs axial (bending or buckling) forces and radial forces.
In accordance with an added feature of the invention, the free end of each of the covers has an inner surface and the support ring has a section which runs at a slight spacing parallel to the inner surface of the free end such that a cylindrical gap is formed there-between. Solder can now be disposed in and fill the cylindrical gap.
In a particular configuration of the invention, the support ring can have an L-shaped cross section whose radial web runs between the edge and the end face of the insulating cylinder and whose axial web runs parallel to and next to the edge, solder being filled into the gap between the axial web and the inner surface of the edge.
At the same time, it is also possible to attach to the support ring a screen that screens the sealing element. It is desirable that the support ring and the screen be formed as a one-piece or integrated unit.
In a particularly advantageous configuration of the invention, the cover can consist of steel; however, it is also possible to provide a cover section which is formed partially from ceramic to which a cup-shaped cover part made from steel is connected. In this case the cover section can be fastened on the insulating cylinder separately therefrom, or it can also be integrally formed on the insulating cylinder.
The shapes of the insulating cylinder are to be constructed and dimensioned such that they are of adequate strength. For this purpose, it is possible in a known way for the ceramic cylinder to have an inwardly drawn arc at each of its two ends; it is also possible to construct the ceramic body in a somewhat bulging fashion overall, and to provide further plates known per se.
In accordance with an additional feature of the invention, the support ring is disposed and constructed from solder, shaped like a fillet, between at least one of an inner surface and an outer surface of the free end of each of the covers and the end face of the insulating cylinder. The solder covers a region of one of the outer surface and the inner surface of the free end which is adequate for absorbing compressive forces.
In accordance with another feature of the invention, the free end of the covers is soldered directly onto the end face of the insulating cylinder.
In accordance with a further added feature of the invention, the support ring is a radially running annular plate formed of copper, and the free end of the covers is fastened with an interposition of the radially running annular plate.
In accordance with a further additional feature of the invention, the annular plate projects into an interior of the vacuum chamber and serves to hold further components including a screen.
In accordance with yet another feature of the invention, the covers are formed of steel and the support ring is formed of copper.
In accordance with a concomitant feature of the invention, the covers each have a cover section formed partially from ceramic and a cup-shaped cover part made from steel connected to the cover section. The cover section has a first part formed in one of a frustoconical and an arcuate shape with a first diameter and an edge, and a second part being a radial section with a second diameter smaller than the first diameter and extending from the edge of the first part. The cup-shaped cover part is fastened to the radial section. The cover section is preferably integrally formed on the insulating cylinder.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a vacuum chamber, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.